//
// DateTime.h
//
// Library: Foundation
// Package: DateTime
// Module:  DateTime
//
// Definition of the DateTime class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_DateTime_INCLUDED
#define Foundation_DateTime_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Timespan.h"
#include "Poco/Timestamp.h"


namespace Poco
{


class Foundation_API DateTime
/// This class represents an instant in time, expressed
/// in years, months, days, hours, minutes, seconds
/// and milliseconds based on the Gregorian calendar.
/// The class is mainly useful for conversions between
/// UTC, Julian day and Gregorian calendar dates.
///
/// The date and time stored in a DateTime is always in UTC
/// (Coordinated Universal Time) and thus independent of the
/// timezone in effect on the system.
///
/// Conversion calculations are based on algorithms
/// collected and described by Peter Baum at
/// http://vsg.cape.com/~pbaum/date/date0.htm
///
/// Internally, this class stores a date/time in two
/// forms (UTC and broken down) for performance reasons. Only use
/// this class for conversions between date/time representations.
/// Use the Timestamp class for everything else.
///
/// Notes:
///   * Zero is a valid year (in accordance with ISO 8601 and astronomical year numbering)
///   * Year zero (0) is a leap year
///   * Negative years (years preceding 1 BC) are not supported
///
/// For more information, please see:
///   * http://en.wikipedia.org/wiki/Gregorian_Calendar
///   * http://en.wikipedia.org/wiki/Julian_day
///   * http://en.wikipedia.org/wiki/UTC
///   * http://en.wikipedia.org/wiki/ISO_8601
{
public:
    enum Months
    /// Symbolic names for month numbers (1 to 12).
    {
        JANUARY = 1,
        FEBRUARY,
        MARCH,
        APRIL,
        MAY,
        JUNE,
        JULY,
        AUGUST,
        SEPTEMBER,
        OCTOBER,
        NOVEMBER,
        DECEMBER
    };

    enum DaysOfWeek
    /// Symbolic names for week day numbers (0 to 6).
    {
        SUNDAY = 0,
        MONDAY,
        TUESDAY,
        WEDNESDAY,
        THURSDAY,
        FRIDAY,
        SATURDAY
    };

    DateTime();
    /// Creates a DateTime for the current date and time.

    DateTime(const Timestamp & timestamp);
    /// Creates a DateTime for the date and time given in
    /// a Timestamp.

    DateTime(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
    /// Creates a DateTime for the given Gregorian date and time.
    ///   * year is from 0 to 9999.
    ///   * month is from 1 to 12.
    ///   * day is from 1 to 31.
    ///   * hour is from 0 to 23.
    ///   * minute is from 0 to 59.
    ///   * second is from 0 to 60 (allowing leap seconds).
    ///   * millisecond is from 0 to 999.
    ///   * microsecond is from 0 to 999.

    DateTime(double julianDay);
    /// Creates a DateTime for the given Julian day.

    DateTime(Timestamp::UtcTimeVal utcTime, Timestamp::TimeDiff diff);
    /// Creates a DateTime from an UtcTimeVal and a TimeDiff.
    ///
    /// Mainly used internally by DateTime and friends.

    DateTime(const DateTime & dateTime);
    /// Copy constructor. Creates the DateTime from another one.

    ~DateTime();
    /// Destroys the DateTime.

    DateTime & operator=(const DateTime & dateTime);
    /// Assigns another DateTime.

    DateTime & operator=(const Timestamp & timestamp);
    /// Assigns a Timestamp.

    DateTime & operator=(double julianDay);
    /// Assigns a Julian day.

    DateTime &
    assign(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microseconds = 0);
    /// Assigns a Gregorian date and time.
    ///   * year is from 0 to 9999.
    ///   * month is from 1 to 12.
    ///   * day is from 1 to 31.
    ///   * hour is from 0 to 23.
    ///   * minute is from 0 to 59.
    ///   * second is from 0 to 60 (allowing leap seconds).
    ///   * millisecond is from 0 to 999.
    ///   * microsecond is from 0 to 999.

    void swap(DateTime & dateTime);
    /// Swaps the DateTime with another one.

    int year() const;
    /// Returns the year.

    int month() const;
    /// Returns the month (1 to 12).

    int week(int firstDayOfWeek = MONDAY) const;
    /// Returns the week number within the year.
    /// FirstDayOfWeek should be either SUNDAY (0) or MONDAY (1).
    /// The returned week number will be from 0 to 53. Week number 1 is the week
    /// containing January 4. This is in accordance to ISO 8601.
    ///
    /// The following example assumes that firstDayOfWeek is MONDAY. For 2005, which started
    /// on a Saturday, week 1 will be the week starting on Monday, January 3.
    /// January 1 and 2 will fall within week 0 (or the last week of the previous year).
    ///
    /// For 2007, which starts on a Monday, week 1 will be the week startung on Monday, January 1.
    /// There will be no week 0 in 2007.

    int day() const;
    /// Returns the day within the month (1 to 31).

    int dayOfWeek() const;
    /// Returns the weekday (0 to 6, where
    /// 0 = Sunday, 1 = Monday, ..., 6 = Saturday).

    int dayOfYear() const;
    /// Returns the number of the day in the year.
    /// January 1 is 1, February 1 is 32, etc.

    int hour() const;
    /// Returns the hour (0 to 23).

    int hourAMPM() const;
    /// Returns the hour (0 to 12).

    bool isAM() const;
    /// Returns true if hour < 12;

    bool isPM() const;
    /// Returns true if hour >= 12.

    int minute() const;
    /// Returns the minute (0 to 59).

    int second() const;
    /// Returns the second (0 to 59).

    int millisecond() const;
    /// Returns the millisecond (0 to 999)

    int microsecond() const;
    /// Returns the microsecond (0 to 999)

    double julianDay() const;
    /// Returns the julian day for the date and time.

    Timestamp timestamp() const;
    /// Returns the date and time expressed as a Timestamp.

    Timestamp::UtcTimeVal utcTime() const;
    /// Returns the date and time expressed in UTC-based
    /// time. UTC base time is midnight, October 15, 1582.
    /// Resolution is 100 nanoseconds.

    bool operator==(const DateTime & dateTime) const;
    bool operator!=(const DateTime & dateTime) const;
    bool operator<(const DateTime & dateTime) const;
    bool operator<=(const DateTime & dateTime) const;
    bool operator>(const DateTime & dateTime) const;
    bool operator>=(const DateTime & dateTime) const;

    DateTime operator+(const Timespan & span) const;
    DateTime operator-(const Timespan & span) const;
    Timespan operator-(const DateTime & dateTime) const;
    DateTime & operator+=(const Timespan & span);
    DateTime & operator-=(const Timespan & span);

    void makeUTC(int tzd);
    /// Converts a local time into UTC, by applying the given time zone differential.

    void makeLocal(int tzd);
    /// Converts a UTC time into a local time, by applying the given time zone differential.

    static bool isLeapYear(int year);
    /// Returns true if the given year is a leap year;
    /// false otherwise.

    static int daysOfMonth(int year, int month);
    /// Returns the number of days in the given month
    /// and year. Month is from 1 to 12.

    static bool
    isValid(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
    /// Checks if the given date and time is valid
    /// (all arguments are within a proper range).
    ///
    /// Returns true if all arguments are valid, false otherwise.

protected:
    static double toJulianDay(Timestamp::UtcTimeVal utcTime);
    /// Computes the Julian day for an UTC time.

    static double
    toJulianDay(int year, int month, int day, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0);
    /// Computes the Julian day for a gregorian calendar date and time.
    /// See <http://vsg.cape.com/~pbaum/date/jdimp.htm>, section 2.3.1 for the algorithm.

    static Timestamp::UtcTimeVal toUtcTime(double julianDay);
    /// Computes the UTC time for a Julian day.

    void computeGregorian(double julianDay);
    /// Computes the Gregorian date for the given Julian day.
    /// See <http://vsg.cape.com/~pbaum/date/injdimp.htm>, section 3.3.1 for the algorithm.

    void computeDaytime();
    /// Extracts the daytime (hours, minutes, seconds, etc.) from the stored utcTime.

private:
    void checkLimit(short & lower, short & higher, short limit);
    void normalize();
    ///utility functions used to correct the overflow in computeGregorian

    Timestamp::UtcTimeVal _utcTime;
    short _year;
    short _month;
    short _day;
    short _hour;
    short _minute;
    short _second;
    short _millisecond;
    short _microsecond;
};


//
// inlines
//
inline Timestamp DateTime::timestamp() const
{
    return Timestamp::fromUtcTime(_utcTime);
}


inline Timestamp::UtcTimeVal DateTime::utcTime() const
{
    return _utcTime;
}


inline int DateTime::year() const
{
    return _year;
}


inline int DateTime::month() const
{
    return _month;
}


inline int DateTime::day() const
{
    return _day;
}


inline int DateTime::hour() const
{
    return _hour;
}


inline int DateTime::hourAMPM() const
{
    if (_hour < 1)
        return 12;
    else if (_hour > 12)
        return _hour - 12;
    else
        return _hour;
}


inline bool DateTime::isAM() const
{
    return _hour < 12;
}


inline bool DateTime::isPM() const
{
    return _hour >= 12;
}


inline int DateTime::minute() const
{
    return _minute;
}


inline int DateTime::second() const
{
    return _second;
}


inline int DateTime::millisecond() const
{
    return _millisecond;
}


inline int DateTime::microsecond() const
{
    return _microsecond;
}


inline bool DateTime::operator==(const DateTime & dateTime) const
{
    return _utcTime == dateTime._utcTime;
}


inline bool DateTime::operator!=(const DateTime & dateTime) const
{
    return _utcTime != dateTime._utcTime;
}


inline bool DateTime::operator<(const DateTime & dateTime) const
{
    return _utcTime < dateTime._utcTime;
}


inline bool DateTime::operator<=(const DateTime & dateTime) const
{
    return _utcTime <= dateTime._utcTime;
}


inline bool DateTime::operator>(const DateTime & dateTime) const
{
    return _utcTime > dateTime._utcTime;
}


inline bool DateTime::operator>=(const DateTime & dateTime) const
{
    return _utcTime >= dateTime._utcTime;
}


inline bool DateTime::isLeapYear(int year)
{
    return (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0);
}


inline void swap(DateTime & d1, DateTime & d2)
{
    d1.swap(d2);
}


} // namespace Poco


#endif // Foundation_DateTime_INCLUDED
